1. Field of the Invention
The invention relates to lithography using a charged particle beam. More specifically, the invention relates to a stage phase measurement method for a charged particle beam exposure apparatus for measuring the phase of a mask stage coordinate system for a specimen stage coordinate system of a charged particle beam exposure apparatus; a demagnification measurement method for a charged particle beam exposure apparatus for measuring the demagnification for image projection onto a mask specimen surface; a control method for a charged particle beam exposure apparatus for performing control corresponding the measured phase and demagnification; and a charged particle beam exposure apparatus.
2. Description of the Related Art
With increasingly fined semiconductor devices, studies and research are being made regarding charged particle beam exposure apparatuses for exposure patterns.
Demagnification lenses and objective lenses are used to demagnify and transferring a mask pattern onto a specimen. The mask pattern is demagnified by these lenses and the pattern is rotated by a magnetic field, so that the phase of the pattern to be transferred onto the surface of the specimen is varied concurrently with deflection in demagnification. The apparatus is designed by taking both the rotation and the demagnification into account, and the apparatus is designed so that the rotation is performed at a desired demagnification. Practically, however, design errors and manufacture errors disable obtaining the condition concurrently allowing the desired demagnification and the desired rotation to be exhibited. A process for measuring the demagnification and pattern rotation angle is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 7-22349.
A rotational error of the pattern is correctable by using a rotation stage that carries the mask. However, since no means is provided to correct the movement direction of a mask stage X and the movement direction of a mask stage Y, the system phase of the mask stage coordinate system remains mismatched with the specimen stage coordinate system.
Because of assembly errors, design errors, and lens system adjustment errors, the mask stage coordinate system has errors for the specimen stage coordinate system; and generally, it does not have means for adjusting the errors. While an XY mask stage should be mounted to one more θ stage to adjust the phase of an XY mask stage, since the construction is thereby completed and free space in an electrooptical housing is insufficient, it is difficult to mount the XY mask stage. When moving a desired mask pattern with the mask stage to the vicinity of the beam, if such errors as those described above are zero, the movement position can be determined in accordance with pattern design values. However, a problem arises in that an accurate movement position of the pattern cannot be known, so that accurate movement cannot be implemented.
Regarding a demagnification measurement method, using a design distance D between two opening portions provided in the mask and a distance d between individual beam specimen surface positions formed in the opening portions, the demagnification has been obtained by way of “demagnification M=d/D”. However, errors such as those occurring in the manufacture of the opening portions and distortion undesirably influence the calculation result. In a case where the manufacture error is 50 nm and the distance between the opening portions is 500 μm, the case results in causing an error of 0.01% (50 nm/500 μm×100). When performing scan-exposure of a 300 μm mask pattern by using the demagnification, there arises the problem of causing an image-dimensional error of as large as 30 nm (i.e., 300 μm×0.01%=30 nm).
Further, a problem arises in that an accurate pattern cannot be imaged onto the specimen since no method is available to measure the phase of the mask stage coordinate system with respect to the problem of demagnification measurement errors and the specimen stage coordinate system.